Assessment of heavy metal accumulation potential of selected cassava varieties cultivated in crude oilimpactedzone,Emuoha,RiversState.

Abstract

This study evaluated the concentration of some heavy metals (cadmium (Cd), chromium (Cr), mercury (Hg), lead (Pb) and asenic (As)) in soil and cassava (TMS 9210326 than TMS 305721) in a crude oil-impacted zone of Omerelu, Rivers State. Soil and cassava samples were collected from four crude oil impacted zones (Omerelu, Eberator,Obelele and Ibaa), processed and analysed for heavy metal concentrations. Results showed that the heavy metals in the soils were higher than those in cassava varieties with the mean values (mg/kg) 11.817  20.4 (Cd), 0.388  0.17 (Cr), 0.395  0.17 (Hg), 0.583  0.32 (Pb), and 0.500  0.12 (As) respectively. The order of heavy metal accumulation in the soil and cassava varieties (Soil> TMS 92/0326 > TMS 305721) differed with Cd having the highest concentration. Mean values of heavy metal were consistently higher in TMS 921.0326 than the TMS
305721 except Pb. Cd value exceeded the permissible safety limit of 0.02 mg/kg and 1.00 mg/kg set by WHO/FAO for crop/food and soil. There was significant difference between all heavy metal absorbed by the two cultivars at p<0.05. There was a very strong positive correlation between Hg and Pb (r = 0.951). Bioaccumulation factor (BAF) for all the heavy metals except Pb were higher in TMS 9210326 than in TMS 305721 with all values less than one signifying lower risk. Cassava farmers should be discouraged from farming on crude oil impacted soil but may use a better resistant variety like TMS 305721 instead as a more resistant variety in these localities.